Visually impaired individuals frequently suffer from reduced vision due to reduced functionality of their retina. Such reduced functionality may be due to damage, and/or to various disease processes which gradually reduce the function of the retina and hence lead to impaired vision over time. One example of such a disease process relates to AMD, or age-related macular degeneration, the leading cause of blindness among adults in the US. The macula is the part of the retina which provides sharply focused images and hence is particularly required for such activities as reading and driving.
AMD poses another challenge, which is that since its effects on the retina are uneven, mainly affecting the macula, such that assistive or corrective devices need to be able to relate to uneven retinal function, which may further vary between individuals. Currently, the most effective devices have involved implants to the eye, but these devices are highly experimental, very invasive and clearly undesirable (from a therapeutic standpoint) in many ways.
Various devices have been proposed which project light directly onto the retina, as disclosed for example in U.S. Pat. No. 5,653,751. However, the described device requires that an optical element be implanted into the eye, which again is highly undesirable as described above.
Some taught devices do not require any implantable element, as described for example in U.S. Pat. No. 7,023,621 to Dietrich; however this device assumes an ideal retina, with entirely homogenous functioning over the entire retina. For a normal, healthy retina, such an assumption, while incorrect, may still yield a reasonably effective device; however, for a retina with reduced function, or otherwise uneven function, such an assumption is not correct and greatly reduces the effectiveness of the device.